Electrical pulse generating apparatus



Jan. 17,19 7 D. UD N 3,299,339

' ELECTRICAL PULSE GENERATING APPARATUS 7 Original Filed June 13, 19571N VEN TOR. pom/91p c. 40000 AT ORNEYS United States Patent 3,299,339ELECTRICAL PULSE GENERATING APPARATUS Donald C. London, Sidney, N.Y.,assignor to The Bendix Corporation, a corporation of DeiawareContinuation of application Ser. No. 665,558, June 13, 1957. Thisapplication Nov. 13, 1362, Ser. No. 236,885 14 Claims. (Cl. 320-41) Thisapplication is a continuation No. 665,558 filed June 13, 1957, for tus,now abandoned.

This invention relates to electrical apparatus and more particularly toelectrical systems adapted for producing electrical impulses forignition purposes.

One of the objects of the present invention is to provide novel means ofsimple construction for controlling the charging and discharging of anelectrical condenser.

Another object of the invention is to provide electrical apparatusincluding a novel circuit having a storage condenser and a load devicesuch as a spark discharge gap fed thereby.

A further object is to provide a novel electrical circuit of the abovetype which is dependable in operation and is adapted for use during longperiods without danger of operating failures.

Still another object is to provide novel electrical apparatus forproducing sparks or arcs, suc as for igniting combustible charges incombustion engines of all types.

Another object is to .provide electrical apparatus of the condenserdischarge type which embodies a novel condenser system and novel meansfor charging the same, the weight and volume of the condenser and of thecharging means being thereby markedly decreased.

A still further object is to provide an electrical circuit having acontrol gap interposed between a storage con denser and an electricalloading device, said circuit incorporating novel means for protectingthe circuit upon the short circuiting thereof, for reducing themagnitude of the peak current through the rectifiers and for increasingthe conduction time through the rectifiers.

Another object is to provide a novel ignition circuit which may beadvantageously incorporated in fuel igniting apparatus which issubjected to high temperatures during use.

The above and further objects and novel features of the presentinvention will more fully appear from the following detailed descriptionwhen the same is read in connect-ion with the accompanying drawings. Itis to be expressly understood, however, that the drawings are for thepurpose of illustration only and are not intended as a definition of thelimits of the invention.

The single figure of he drawing is a diagram illustrating one form ofelectrical circuit embodying the invention.

The embodiment of the invention illustrated in the accompanying drawingis, by way of example, shown in the form of a circuit for apparatusadapted for use as an ignition system in combustion engines andso-called jet and gas turbine engines. A particular use in which suchapparatus and circuit have been found advantageous is in an ignitionsystem for a ramjet engine wherein the weight and volume of the ignitionsystem are desirably held to a minimum. The ignition system for a ramjetengine should also be rugged and free from tendencies to becomeshort-circuited at high temperatures since usually the ignition systemof such engine is subjected to elevated temperatures during use. Asabove pointed out, however, the invention is not limited to such use,since it is capable of use in various other applications.

As shown in the drawing, one suitable embodiment of the inventioncomprises, as a source of electrical energy, an alternating currentgenerator which may be conof application Serial Electrical Appara-3,299,339 Patented Jan. 17, 1967 nected to the remainder of the circuitby means of a switch 11 interposed in one of the supply leads to thecircuit. Generator 10 is connected by means, such as a plug 12, to theinput of the electrical impulse generating device of the invention,which is conveniently supplied as a unit designated 14. Preferably suchunit is contained in a metallic casing which may be grounded asindicated.

Unit 14 includes a suitable filtering means 16 in each side of thesupply circuit, means 16 being useful, for example, when the generator10 supplies other circuits, so as to prevent radio frequencies fromfeeding back from unit- 14 into other circuits powered by the generator.In the particular embodiment shown, the filter means comprises by-passcondensers connected between ground (which may be the shielded case ofunit 14) and each power supply line, there being an inductanceinterposed in each such power supply line and between the by-passcondensers. The filters are conveniently contained in a sub-housingdesignated 15. Such filters, which are conventional, form no part of thepresent invention. The power supply lines beyond filters 16, 16 aredesignated 17 and 19.

The wires 17 and 19 are connected to the opposite ends of the primary 23of voltage step-up power transformer 20. The secondary 28 of transformer20 charges a condenser system or bank 33 in a step-by-step manner untilthe condenser bank reaches the potential at which control gap 39discharges. The control gap then feeds its output through lead 40 towire 42 connected to unit 14 by plug 41, and thence to a load which inthis instance is a spark discharge device 44. In the embodiment shown,device 44 has a spark gap '45 which is shunted by a resistance 46 whichmay be in the form of a semi-conductive surface at the spark gap. Theother side of device 44 is connected to ground through lead 47.

Transformer 20 is preferably of the so-called reactancetype having highsecondary leakage inductance characteristics, or, in other words,wherein the primary and secondary are loosely coupled and there is alarge leakage flux, the degree of which is governed by the secondaryload conditions. In such transformer, as the secondary load currentincreases the secondary terminal voltage drops. In the embodiment showna first lead 21 from secondary 28 of transformer 20 has a first set 24of serially connected rectifiers interposed therein in advance of thecontrol gap 39. A second set of rectifiers, designated 25, which areconnected reversely from rectifiers 24, are connected to wire 21 betweenthe secondary 28 of the transformer and rectifier set 24 by a wire 38.The other end of rectifier set 25 is connected to ground through aserially connected resistance 26 and a wire 27. A wire 29, connected towire 21 between rectifier bank 24 and control gap 39 has two seriallyconnected condensers 30 and 31 interposed therein. A wire 32 connectscondenser 31 to ground. A wire 35, connected to wire 29 between wire 21and condenser 30, has a condenser 36 interposed therein. The condenser36 is connected to ground by wire 37. The second lead 34 from secondary28 of transformer 20 is connected to wire 29 between condensers 30 and31.-

Condensers 30 and 31 are Preferably condenser 36 has a capacity on theorder of times that of either condensers'3ti or 31. "The describedfirst, second and third condensers 30, 31, and j 36, respectively,function together as a tank condenser preferably of small, equalcapacity. Condenser 36 is preferably of much'larger capacity than thatof each of condensers 30 and 31.

denser 3f). When'condenser bank 33 is charged by rectifier 25,condensers 30 and 36 are in effect connected in series, suchserially-connected condensers being connected in parallel with condenser31. Such operation of the system results from the facts that wires 27,32, and 37 are in effect connected together, since they are allconnected to ground, and that the resulting circuit is alternately fedwith charging current through wires 29 and 27. After the condensers 30,31, and 36 have been charged step-by-step in the manner describedto apredetermined voltage, which may be relatively low, e.g. on the order of3000 volts, the discharge gap of device 39 breaks down and thecondensers discharge as a unit through gap 39 into spark gap 44todischarge the latter, following which the charging of condenser system33 is repeated.

By reason of the described connection of condensers 30, 31, and 36,there is obtained both a doubling of the voltage impressed uponcondenser system 33 and a marked saving in weight and space required toyield a given desired capacity. This effects a marked saving in theweight and volume of the capacitor requiredfor the operation of thedevice. Such saving will be appreciated upon the consideration of thefollowing example set-ting forth typical values of the condensers in thecondenser bank or system 33. In such example, condensers 30 and 31 eachhas a capacity of .02 mfd., and condenser 36 has a capacity of 2 mid.The total capacity of seriesconnected condensers is, of course, given bythe formula 1/C.=1/c +1/c =1/c etc. The total capacity of condensersconnected in parallel is given by the formula C=c +c +c etc. The totaleffective capacity on discharge of condenser system 33 may thus becalculated to be 2.01 mfd. If the same voltage and total capacity wereto be obtained from the two condensers 30, 31, without condenser 36,each of condensers 30, 31 would necessarily have a capacity ofabdut 4mfd.

The transformer functions as a choke oil to determine to a materialextent the rate of flow of current from the discharge electrode ofdevice 39. I The loosely coupled reactance-type transformer 20 deliversonly a limited amount of power due to its high secondary leakageinductance. Consequently, it effectively controls the charging rate ofthe condenser system and regulates the spark-producing rate of theapparatus, as well as reducing the magnitude of the peak current throughthe rectifiers and increasing the conduction time of such rectifiers. Ithas been found that, when such reactance-type transformer is used, noother regulating elements need be employed in the circuit.v Theresistance 26, which is preferably used in the circuit, limits thecurrent which flows through rectifier sets 24 and 25 in series shouldcondenser 36 attain a negative potential during discharge. Thus, suchresistance protects the rectifiers from overload.

The circuit of the invention makes possible the production of highenergy sparks at discharge device 44 with a substantial decrease in thetotal capacity of the condensers employed. Such saving in totalcapacitance required, and thus in the weight and volume of the ignitionunit, is particularly marked when the described reactance-type powertransformer is employed in the circuit. The circuit of the invention issimple and easily maintained. It eliminates the necessity for currentcontrol devices other than the reactance-type power transformer. It alsoallows the use of much smaller condensers in the circuit than if aconventional close coupled power transformer were .used. Thus, with suchlatter type of transformer, condensers and 31 must each be of 4 mfd.capacity in order that the circuit may operate in a manner comparable tothat of the circuit of the invention.

Although only one embodiment of the invention has been illustrated inthe accompanying drawing and described in the foregoing specification,it is to be'expressly understood that the invention is not limitedthereto but that it may be embodied in other specifically definedcircuits. For example, other well known sources of pulsating oralternating current may be provided in lieu of the generator-transformercombination illustrated. Wires 27, 32, and 37 may be actually physicallyconnected together by a wire, rather than all being connected to ground.Additionally, the various parts of the circuit may be rearranged withrespect to each other without appreciably affecting the operation of thecircuit. Various other changes may also be made, such as the electricalvalues suggested herein, by way of example, without departing from thespirit and scope of the invention, as the latter will now be understoodby those skilled in the art. A

What is claimed is:

1. In electrical apparatus having a storage condenser, 21 load circuitconnected to be fed by the storage condenser, and a control gapinterposed between the storage condenser and the load circuit, theimprovement which comprises a multiple condenser system forming saidstorage condenser, said system having a first and a second condenserconnected in series and a third condenser connected in parallel withsaid series-connected first and second condensers, said first and secondcondensers being of substantially equal capacity and said thirdcondenser having a capacity which is relatively large compared to thatof either the first or second condenser, a source of current producingpulses of alternating polarity, means to esta'blish a first chargingcircuit electrically connecting a first side of said source to thecondenser system between the first and second condensers and the otherside of said source between the first and third condensers at eachpositive pulse of the'current source, and means to establish a secondcharging circuit electrically connecting said first side of the currentsource to the condenser system between the firs-t and second condensersand the other side of said source between the second and thirdcondensers at each negative pulse of the current source.

2. In electrical apparatus having a storage condenser, a load circuitconnected to be fed by the storage can denser, and a control gapinterposed between the storage condenser and the load circuit, theimprovement which comprises a multiple condenser system forming saidstorage condenser, said system having a circuit with a first and asecond condenser connected in series and a third condenser connected inparallel with said series-connected first and second condense-rs, asource of alternating current comprising a loosely coupled transformerhaving a large leakage flux, one side of said source being connected tothe condenser system between and to the first sides of, the first andsecond condensers, additional circuits connecting the other side of thesource to the condenser system at the second sides of the first andsecond condensers, and reversely connected half-wave rectifiersinterposed in each of said additional circuits.

3. In electrical apparatus having a storage condenser, a load circuitconnected to be fed by the storage condenser, and a control gapinterposed between the storage condenser and the load circuit, theimprovement which comprises a multiple condenser system forming saidstorage condenser, said system having a circuit with a first and asecond condenser connected in series and a third condenser connected inparallel with said series-connected first and second condensers, saidfirst and second condensers being of substantially equal capacity andsaid third condenser having a capacity which is relatively largecompared to that of either the first or second condenser, a source ofalternating current, one side of said source being connected to thecondenser system between, and to the first sides of, the first andsecond condensers, additional circuits connecting the other side of thesource to the condenser system at the second sides of the first andsecond condensers, and reversely connected half-wave rectifiersinterposed in each of said additional circuits.

4. In electrical apparatus having a storage condenser,

S a load circuit including a spark gap connected to be fed by thestorage condenser, and a control gap interposed between the storagecondenser and the load circuit, the improvement which comprises amultiple condenser system forming said storage condenser, said systemhaving a circuit with a first and a second condenser of substan tiallythe same small capacity connected in series and a third condenser ofmarkedly larger capacity connected in parallel with saidseries-connected first and second condensers, a source of alternatingcurrent, one side of said source being connected to the condenser systembetween and to the first sides of the first and second condensers,additional circuits connecting the other side of the source to thecondenser system at the second sides of the first and second condensers,and reversely connected half-wave rectifiers interposed in each of saidadditional circuits.

5. Electrical apparatus as defined in claim 4, wherein the source ofalternating current is a reactance-type transformer.

6. In electrical apparatus having a storage condenser, a load circuitconnected to be fed by the storage condenser, and means interposedbetween the storage condenser and the load circuit for controlling thedischarge of the condenser, the improvement which comprises a multiplecondenser system forming said storage condenser, said system having afirst and a second condenser connected in series and a third condenserconnected in parallel with said series-connected first and secondcondensers, said third condenser having a capacity which is relativelylarge compared to the capacity of either the first or second condenser,a source of current producing pulses of alternating polarity, means toestablish a first charging circuit electrically connecting a first sideof said source to the condenser system between the first and secondcondensers and the other side of said source between the first and thirdcondensers at each positive pulse of the current source and means toestablish a second charging circuit electrically connecting said firstside of the current source to the condenser system between the first andsecond condensers and the other side of said source between the secondand third condensers at each negative pulse of the current source.

7. Electrical apparatus as defined in claim 6, wherein the first andsecond condensers are of substantially equal capacity.

8. Electrical apparatus as defined in claim 6, comprising rectifiermeans in each charging circuit to prevent reverse flow of currenttherethrough.

9. Electrical apparatus as defined in claim 8, comprising electricalresistance interposed in said charging circuits, said resistance beingof sufiicient value to protect said rectifiers from overload during thedischarging of said condensers.

10. In electrical apparatus having a storage condenser, a load circuitconnected to be fed by the storage condenser, and means interposedbetween the storage condenser and the load circuit for controlling thedischarge of the condenser, the improvement which comprises a multiplecondenser system forming said storage condenser, said system having acircuit with a first and a second condenser connected in series and athird condenser connected in parallel with said series-connected firstand second condensers, said third condenser having a capacity which isrelatively large compared to that of either the first or secondcondenser, a source of alternating current, one side of said sourcebeing connected to the condenser system between, and to the first sidesof, the first and second condensers, and additional circuits connectingthe other side of the source to the condenser system at the second sidesof the first and second condensers, and reversely connected half-waverectifiers interposed in each of said additional circuits.

11. Electrical apparatus as defined in claim 10, wherein the source ofalternating current comprises a loosely coupled transformer having alarge leakage flux and a secondary winding to which said condensersystem is connected.

12. Electrical apparatus as defined in claim 10, wherein the first andsecond condensers are of substantially equal capacity.

13. Electrical apparatus as defined in claim 10, comprising a resistanceinterposed in said additional circuits, said resistance being ofsulficient value to protect said rectifiers from overload during thedischarging of said condensers.

14. Electrical apparatus comprising in combination a storage condenser,a load circuit connected to be fed by the storage condenser, meansinterposed between the storage condenser and the load circuit forcontrolling the discharge of the storage condenser, the latter being inthe form of a multiple condenser system, said system having a first anda second condenser connected to the load circuit in series and a thirdcondenser connected in parallel with said series connected first andsecond condensers, a source of alternating current including a looselycoupled transformer having a large leakage flux, one side of said sourcebeing connected to the condenser system between and to the first sidesof the first and second condensers, additional circuits connecting theother side of the source to the condenser system at the second sides ofthe first and second condensers, and reversely connected half-waverectifiers interposed in each of said additional circuits.

References Cited by the Examiner UNITED STATES PATENTS 2,136,895 11/1938Sola 336- 2,536,143 l/l951 Short 320l 2,589,164 3/1952 Tognola 3l5-223BERNARD KONICK, Primary Examiner. IRVING SRAGOW, Examiner.

M. S. GITTES, Assistant Examiner.

1. IN ELECTRICAL APPARATUS HAVING A STORAGE CONDENSER, A LOAD CIRCUITCONNECTED TO BE FED BY A STORAGE CONDENSER, AND A CONTROL GAP INTERPOSEDBETWEEN THE STORAGE CONDENSER AND THE LOAD CIRCUIT, THE IMPROVEMENTWHICH COMPRISES A MULTIPLE CONDENSER SYSTEM FORMING SAID STORAGECONDENSER, SAID SYSTEM HAVING A FIRST AND A SECOND CONDENSER CONNECTEDIN SERIES AND A THIRD CONDENSER CONNECTED IN PARALLEL WITH SAIDSERIES-CONNECTED FIRST AND SECOND CONDENSERS, SAID FIRST AND SECONDCONDENSERS BEING OF SUBSTANTIALLY EQUAL CAPACITY AND SAID THIRDCONDENSER HAVING A CAPACITY WHICH IS RELATIVELY LARGE COMPARED TO THATOF EITHER THE FIRST OR SECOND CONDENSER, A SOURCE OF CURRENT PRODUCINGPULSES OF ALTERNATING POLARITY, MEANS TO ESTABLISH A FIRST CHARGINGCIRCUIT ELECTRICALLY CONNECTING A FIRST SIDE OF SAID SOURCE TO THECONDENSER SYSTEM BETWEEN THE FIRST AND SECOND CONDENSERS AND THE OTHERSIDE OF SAID SOURCE BETWEEN THE FIRST AND THIRD CONDENSERS AT EACHPOSITIVE PULSE OF THE CURRENT SOURCE, AND MEANS TO ESTABLISH A SECONDCHARGING CIRCUIT ELECTRICALLY CONNECTING SAID FIRST SIDE OF THE CURRENTSOURCE TO THE CONDENSER SYSTEM BETWEEN THE FIRST AND SECOND CONDENSERSAND THE OTHER SIDE OF SAID SOURCE BETWEEN THE SECOND AND THIRDCONDENSERS AT EACH NEGATIVE PULSE OF THE CURRENT SOURCE.